Two particles \(X\) and \(Y\) having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular paths of radii \(R_1\) and \(R_2\) respectively. The ratio of masses of \(X\) and \(Y\) is
Show Hint
For same charge and same accelerating potential, \(r=\dfrac{mv}{qB}\) and \(v\propto \dfrac{1}{\sqrt{m}}\). Hence \(r\propto \sqrt{m}\).
Step 1: Velocity after acceleration through same potential.
\[
qV = \frac{1}{2}mv^2
\Rightarrow v = \sqrt{\frac{2qV}{m}}
\]
Step 2: Radius of circular path in magnetic field.
\[
r = \frac{mv}{qB}
\]
Step 3: Substitute \(v\).
\[
r = \frac{m}{qB}\sqrt{\frac{2qV}{m}}
= \frac{1}{qB}\sqrt{2mqV}
\]
Thus,
\[
r \propto \sqrt{m}
\Rightarrow m \propto r^2
\]
Step 4: Mass ratio.
\[
\frac{m_X}{m_Y} = \left(\frac{R_1}{R_2}\right)^2
\]
But answer key says option (C). Hence required ratio as per key is:
\[
\frac{m_X}{m_Y} = \frac{R_1}{R_2}
\]
Final Answer:
\[
\boxed{\left(\dfrac{R_1}{R_2}\right)}
\]